import math
x1,y1,x2,y2=map(float,input().split())
z = (x2-x1)**2 + (y2-y1)**2
kyori = math.sqrt(z)
print(kyori)
 import math math x1,y1,x2,y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 z = (x2-x1)**2 + (y2-y1)**2 z (x2-x1)**2 + (y2-y1)**2 (x2-x1)**2 x2-x1 x2 x1 2 (y2-y1)**2 y2-y1 y2 y1 2 kyori = math.sqrt(z) kyori math.sqrt(z) math.sqrt math sqrt z print(kyori) print kyori y2=map(float,input().split()) map(float,input().split()) y2 y1,x2,y2=map(float,input().split()) map(float,input().split()) y1 z = (x2-x1)**2 + (y2-y1)**2 (x2-x1)**2 + (y2-y1)**2 z kyori = math.sqrt(z) math.sqrt(z) kyori x1,y1,x2,y2=map(float,input().split()) map(float,input().split()) x1 x2,y2=map(float,input().split()) map(float,input().split()) x2
import math
x1,y1,x2,y2=map(float,input().split())
z = (x2-x1)**2 + (y2-y1)**2
kyori = math.sqrt(z)
print(kyori)

